Composite semipermeable membrane and its manufacturing method

Abstract

A composite semipermeable membrane having a porous support layer and a separation functional layer located on the porous support layer, the surface of the composite semipermeable membrane having: a first surface, which is a surface in the direction of the separation functional layer relative to the porous support layer; and a second surface, which is a surface opposite to the first surface, the separation functional layer containing cross-linked polyamide, the cross section of the separation functional layer in the thickness direction as observed by a scanning transmission electron microscope is divided into two equal parts: region a on the first surface side and region b on the second surface side, when the proportion of coarse pores with a pore size of 0.7 nm or more in region a is set as A, and the proportion of coarse pores with a pore size of 0.7 nm or more in region b is set as B, A / B is 1.40 or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite semipermeable membrane useful for selective separation of a liquid mixture and a method for producing the same. In addition, the present application also relates to a composite semipermeable membrane element provided with the above-described composite semipermeable membrane, and a composite semipermeable membrane module provided with the composite semipermeable membrane element. Furthermore, the present application also relates to a method for producing ultra-pure water using the above-described composite semipermeable membrane. BACKGROUND

[0002] With respect to separation of a mixture, techniques for removing a substance (e.g., a salt) dissolved in a solvent (e.g., water) are various. In recent years, the use of membrane separation methods is expanding as a process for energy saving and resource saving.

[0003] As a membrane used for a membrane separation method, for example, a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, and the like can be cited. These membranes are used for, for example, a manufacturing use for obtaining drinking water or industrial ultra-pure water from seawater, brackish water, water containing harmful substances, and the like, a wastewater treatment use, a valuable substance recovery use, and the like.

[0004] Currently marketed reverse osmosis membranes and nanofiltration membranes are mostly composite semipermeable membranes. Among them, a composite semipermeable membrane in which a separation function layer containing a crosslinked aromatic polyamide obtained by polycondensation of a polyfunctional amine and a polyfunctional acyl halide is coated on a microporous support membrane is widely used as a separation membrane having high water production and salt and neutral molecule selectivity (Patent Literature 1).

[0005] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: International Publication No. 2010 / 096563 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION However, in the conventional composite semipermeable membrane, in the case where neutral molecules contained in raw water are removed, the water production and the selectivity are insufficient, and there is a problem in terms of membrane performance.

[0007] Therefore, an object of the present application is to provide a composite semipermeable membrane excellent in permeated water amount and neutral molecule removal.

[0008] MEANS FOR SOLVING THE PROBLEMS In order to solve the above-described problems, the present application includes the following [1] to

[14] .

[0009] [1] A composite semipermeable membrane which is a composite semipermeable membrane having a porous support layer and a separation function layer on the porous support layer, The composite semipermeable membrane has a first surface which is the surface of the side on which the separation functional layer is present with respect to the porous support layer, and a second surface which is the surface of the side opposite the first surface, The separation functional layer contains a crosslinked polyamide, When the thickness direction cross section of the separation functional layer observed by a scanning transmission electron microscope is bisected into a region a on the first surface side and a region b on the second surface side, and the proportion of the coarse pores having a pore diameter of 0.7 nm or more in the region a is set as A and the proportion of the coarse pores having a pore diameter of 0.7 nm or more in the region b is set as B, A / B is 1.40 or less.

[0010] [2] The composite semipermeable membrane according to the above [1], wherein the proportion A of the coarse pores is 0.10 or less.

[0011] [3] A composite semipermeable membrane which is a composite semipermeable membrane having a porous support layer and a separation functional layer on the porous support layer, The composite semipermeable membrane has a first surface which is the surface of the side on which the separation functional layer is present with respect to the porous support layer, and a second surface which is the surface of the side opposite the first surface, The separation functional layer contains a crosslinked polyamide, In the thickness direction cross section of the separation functional layer, the ratio Nd / Nf of the carboxyl densities measured by a scanning transmission electron microscope is 2.1 or less, Nd: carboxyl density of region d Nf: carboxyl density of region f Regions d and f: regions contained in regions c to g obtained by five-division of the thickness direction cross section of the separation functional layer in the thickness direction of the separation functional layer, and regions c to g are arranged from the first surface toward the second surface.

[0012] [4] The composite semipermeable membrane according to the above [3], wherein the Nd is 2.3 x 10 -26 mol / nm 2 Hereinafter, and the Nf is 0.7 x 10 -26 mol / nm 2 or more.

[0013] [5] The composite semipermeable membrane according to any one of the above [1] to [4], wherein when the amount of terminal amino groups of the crosslinked polyamide is set as C, the amount of terminal carboxyl groups is set as D, and the amount of amide groups is set as E, E / (C+D) is 1.7 or more.

[0014] [6] The composite semipermeable membrane according to any one of [1] to [5] above, wherein the static contact angle of water on the surface of the separation function layer is 40 degrees or more and 120 degrees or less.

[0015] [7] A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of [1] to [6] above.

[0016] [8] A composite semipermeable membrane module comprising the composite semipermeable membrane element according to [7] above.

[0017] [9] A method for producing a composite semipermeable membrane, which is a method for producing a composite semipermeable membrane comprising a support membrane having a base material and a porous support layer, and a separation function layer provided on the porous support layer, the separation function layer being formed by interfacial polycondensation of a polyfunctional amine aqueous solution and a polyfunctional acid halide solution on the porous support layer, the polyfunctional amine aqueous solution comprising a polyfunctional amine, a monofunctional amine having a molecular weight of 150 or less, and a water layer additive having an amide group or a urea group, the polyfunctional acid halide solution comprising a polyfunctional acid halide and an organic solvent.

[0018]

[10] The method for producing a composite semipermeable membrane according to [9] above, wherein the monofunctional amine has a molecular weight of 100 or less.

[0019]

[11] The method for producing a composite semipermeable membrane according to [9] or

[10] above, wherein the moisture content in the organic solvent is 10 ppm or more and 50 ppm or less.

[0020]

[12] The method for producing a composite semipermeable membrane according to any one of [9] to

[11] above, wherein the concentration of the monofunctional amine in the polyfunctional amine aqueous solution is 0.01 mass% or more and 10 mass% or less.

[0021]

[13] The method for producing a composite semipermeable membrane according to any one of [9] to

[12] above, wherein the concentration of the water layer additive in the polyfunctional amine aqueous solution is 0.01 mass% or more and 10 mass% or less.

[0022]

[14] A method for producing ultrapure water, which comprises a reverse osmosis process for removing silica from a silica-containing aqueous solution using the composite semipermeable membrane according to any one of [1] to [6] described above.

[0023] Effects of the Invention According to the present application, a composite semipermeable membrane which realizes both a high permeate water amount and a high removal of neutral molecules can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 ] Figure 1 A schematic diagram showing a cross section of a composite semipermeable membrane according to an embodiment of the present application.

[0025] [Patent Document 1] Figure 2 [Patent Document 2] Figure 2 A schematic diagram showing a cross section of a pleat structure in a separation functional layer.

[0026] [Patent Document 3] Figure 3 [Patent Document 4] Figure 3 A schematic diagram for explaining a method for measuring 10-point average surface roughness.

[0027] [Patent Document 5] Figure 4 [Patent Document 6] Figure 4 A schematic diagram showing a state when a water droplet is added to a surface of a separation functional layer.

[0028] [Patent Document 7] Figure 5 [Patent Document 8] Figure 5 A schematic diagram showing regions a, b in a cross section in a thickness direction of a separation functional layer.

[0029] [Patent Document 9] Figure 6 [Patent Document 10] Figure 6 A schematic diagram showing regions c, d, e, f, g in a cross section in a thickness direction of a separation functional layer.

[0030] [Patent Document 11] Figure 7 [Patent Document 12] Figure 7 A flowchart showing a procedure of a method for producing ultrapure water according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present application will be described in detail, but the present application is not limited to any of these embodiments.

[0032] Note that in the present specification, "mass" is synonymous with "weight".

[0033] (1) Composite semipermeable membrane As shown in FIG. 1, a composite semipermeable membrane 1 according to the present embodiment has a porous support layer 3 and a separation functional layer 4 on the porous support layer 3. In the surface of the composite semipermeable membrane 1, the surface on the side where the separation functional layer 4 is present with respect to the porous support layer 3 is referred to as a first surface 11, and the surface on the opposite side of the first surface 11 is referred to as a second surface 12. Figure 1 The composite semipermeable membrane according to the present embodiment includes a first embodiment satisfying the following condition 1 and a second embodiment satisfying the following condition 2.

[0034] Condition 1: With respect to the separation functional layer, the A / B described later is 1.40 or less in terms of the proportion of macrovoids.

[0035] ​​

[0036] Condition 2: With respect to the separation functional layer, the Nd / Nf described later is 2.1 or less in terms of carboxyl group density.

[0037] The composite semipermeable membrane of any of the embodiments is excellent in water permeation amount and removal of neutral molecules by having a structure in which the polyamide structure in the vicinity of the surface layer of the separation functional layer is denser than the polyamide structure in the inner layer to some extent. Note that the composite semipermeable membrane according to the present embodiment satisfies at least one of Condition 1 and Condition 2, and can satisfy both. In the present specification, the "composite semipermeable membrane according to the present embodiment" includes both the first embodiment and the second embodiment unless otherwise specified.

[0038] (1-1) Separation Functional Layer (1-1-1) Composition Among the constituent elements of the composite semipermeable membrane, the separation functional layer has a solute separation function. The separation functional layer is a layer that separates a solute from a solvent. Figure 1 In the cross-sectional view of the composite semipermeable membrane shown in FIG. 1, the separation functional layer 4 is disposed on the porous support layer 3.

[0039] The separation functional layer of the composite semipermeable membrane according to the present embodiment contains a cross-linked polyamide. The "cross-linked polyamide" refers to a polycondensate of a polyfunctional amine and a polyfunctional acyl halide. Since the chemical stability to acids and bases is high, the separation functional layer preferably contains a cross-linked polyamide as a main component. Here, the "main component" refers to a component that accounts for 50% by mass or more of the constituent components.

[0040] The cross-linked polyamide is preferably formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional acyl halide. In addition, at least one of the polyfunctional amine and the polyfunctional acyl halide preferably contains a compound having 3 or more functional groups.

[0041] The "polyfunctional amine" refers to an amine having at least 2 primary and / or secondary amino groups in one molecule, at least one of which is a primary amino group. As the polyfunctional amine, for example, there are polyfunctional aromatic amines such as phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine, and the like, which have 2 amino groups bonded to a benzene ring in any of the ortho, meta, or para positions; aliphatic amines such as ethylenediamine, propylenediamine, and the like; alicyclic polyfunctional amines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, 4-aminopiperidine, 4-aminoethylpiperazine, and the like.

[0042] Among them, from the viewpoint of the removal performance, the permeated water amount, and the heat resistance of the composite semipermeable membrane, the polyfunctional amine is preferably a polyfunctional aromatic amine having 2 or more and 4 or less primary amino groups and / or secondary amino groups in one molecule. As such a polyfunctional aromatic amine, for example, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, and the like can be given. Among them, from the viewpoint of the easiness of obtaining or the easiness of handling, m-phenylenediamine (hereinafter referred to as "m-PDA") is more preferable.

[0043] These polyfunctional amines can be used alone or two or more kinds thereof can be used simultaneously. When two or more kinds thereof are used simultaneously, the above-mentioned amines can be combined with each other, or the above-mentioned amines can be combined with an amine having at least 2 secondary amino groups in one molecule. As the amine having at least 2 secondary amino groups in one molecule, for example, piperazine, 1,3-bis-piperidinylpropane, and the like can be given.

[0044] The "polyfunctional acid halide" refers to an acid halide having at least 2 halogenated carboxyl groups in one molecule. As the 3-functional acid halide, for example, trimesoyl chloride (hereinafter "TMC"), 1,3,5-cyclohexanetricarbonyl chloride, 1,2,4-cyclobutanetricarbonyl chloride, and the like can be given. As the 2-functional acid halide, for example, aromatic 2-functional acid halides such as biphenyldicarbonyl chloride, azobenzenedicarbonyl chloride, terephthaloyl chloride, isophthaloyl chloride, naphthalenedicarbonyl chloride, aliphatic 2-functional acid halides such as adipoyl chloride, sebacoyl chloride, or alicyclic 2-functional acid halides such as cyclopentanedicarbonyl chloride, cyclohexanedicarbonyl chloride, tetrahydrofuranedicarbonyl chloride, and the like can be given.

[0045] From the viewpoint of the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride. In addition, from the viewpoint of the removal performance and the heat resistance of the composite semipermeable membrane, the polyfunctional acid halide is more preferably a polyfunctional aromatic acid chloride having 2 or more and 4 or less carbonyl chloride groups in one molecule. Among them, from the viewpoint of the easiness of obtaining and the easiness of handling, TMC is further preferable. These polyfunctional acid halides can be used alone or two or more kinds thereof can be used simultaneously.

[0046] The separation functional layer of the composite semipermeable membrane according to the present embodiment preferably has a pleated structure. The "pleated structure" refers to a structure in which Figure 2 protrusions repeatedly exist. Here, the "protrusion" refers to a portion (a recess of the separation functional layer) that is adjacent to each other in the pleated structure of the separation functional layer and protrudes toward the porous support layer, as shown in Figure 2 Here, the "protrusion" refers to a portion (a recess of the separation functional layer)

[0047] From the viewpoint of obtaining sufficient separation performance and water permeation, the thickness of the separation functional layer in the pleated structure (hereinafter also referred to as "pleat thickness") is preferably 8.0 nm or more and 20.0 nm or less, more preferably 9.0 nm or more and 13.0 nm or less.

[0048] The thickness of the wrinkles, as described in the “Forming Process of Separation Functional Layer” described later, can be controlled, for example, by the concentration of the polyfunctional amine and polyfunctional acyl halide as monomers, and the amount of polyfunctional acyl halide solution applied relative to the surface area of ​​the porous support layer.

[0049] Regarding the thickness of the wrinkles, a transmission electron microscope (TEM) can be used to photograph the cross-section of the wrinkled structure. The cross-sectional images are then imported into image analysis software for analysis and measurement. Specifically, five protrusions are randomly selected from the TEM image of the cross-section of the separated functional layers. At each protrusion ( Figure 2 In the attached figures (reference numerals 21 and 22), the distance from the apex of the protrusion to the height ( Figure 2 The fold thickness is determined at 10 points in the area marked by reference numerals 23 and 24 (hereinafter also referred to as "convex height") within 9 of the area. Figure 2 (See figure 27). That is, as shown in the attached figure. Figure 2 As shown, the surface of the porous support layer is set to 0% height, and the apex of the protrusion is set to 100% height. Ten measurement points are randomly selected within the height range of 10% to 100%. The arithmetic mean of the thicknesses obtained from these 50 points is called the "wrinkle thickness". Here, when calculating the wrinkle thickness, the protrusion being measured is defined as a protrusion with a height of at least one-fifth of the average surface roughness of the 10 points.

[0050] The average surface roughness at 10 points is calculated as follows. The cross-section along the thickness direction of the separated functional layer is observed using an electron microscope. The preferred magnification is 10,000 to 100,000 times. In the obtained cross-sectional image, as shown... Figure 3 As shown, the surface of the separated functional layer 4 exhibits a wrinkled curve with continuously repeating convex and concave sections. Regarding this curve, a roughness curve is derived based on the definition in JIS B0601:2013 (ISO4287:1997). A cross-sectional image is extracted with a width of 2.0 μm along the direction of the average line X of the aforementioned roughness curve, using the reference length L as the reference length.

[0051] Based on the average line of the extracted portion, calculate the average absolute value of the elevation (Yp1~5) of the peaks from the highest peak to the fifth peak of the roughness curve, and the sum of the average absolute values ​​of the elevation (Yv1~5) of the valleys from the lowest valley to the fifth valley. Express this value in nanometers (nm) as the 10-point average surface roughness.

[0052] It should be noted that the average line refers to a straight line based on the definition in ISO 4287:1997, which is a straight line drawn in such a way that the sum of the areas enclosed by the average line and the roughness curve in the measured length L is equal above and below the average line.

[0053] From the viewpoint of obtaining sufficient water permeation, the intermediate value of the height of the protrusion of the separation functional layer in the composite semipermeable membrane of this embodiment is preferably 80 nm or more and 300 nm or less, more preferably 120 nm or more and 300 nm or less, and even more preferably 160 nm or more and 300 nm or less.

[0054] The median value of the convex height is calculated as follows. For the composite semi-permeable membrane, when 10 cross-sections are randomly observed, the convex height of all convex parts at least one-fifth of the average surface roughness of the aforementioned 10 points is measured in each cross-section. Then, based on the calculation results for the 10 cross-sections, the median value is calculated, thereby determining the median value of the convex height. Here, each cross-section has a width of 2.0 μm in the direction of the average line of the aforementioned roughness curve.

[0055] The height of the protrusions in the separation functional layer can be controlled, for example, by adding an additive that can interact with polyfunctional amines through hydrogen bonds to the aqueous layer or organic layer during the formation process of the separation functional layer, and by adjusting the diffusion of polyfunctional amines in the organic layer.

[0056] The static contact angle of water on the surface of the separation functional layer of the composite semi-permeable membrane according to this embodiment is preferably 40 degrees or more and 120 degrees or less. Here, "static contact angle of water" is a parameter representing the wettability and hydrophilicity of the surface of the separation functional layer; a smaller contact angle indicates higher hydrophilicity. In the composite semi-permeable membrane according to this embodiment, the proportion of large pores or the carboxyl group density of the surface layer is reduced by the reaction of monofunctional amines near the surface of the separation functional layer, thereby increasing hydrophobicity. From the viewpoint of simultaneously achieving the water permeation and removal performance of the composite semi-permeable membrane, a static contact angle of 60 degrees or more and 100 degrees or less is more preferable.

[0057] like Figure 4 As shown, when a water droplet is added to the surface of the separation functional layer, the water forms a spherical shape due to surface tension, and the following equation (1), known as the "Young's Equation", holds.

[0058] γ S =γ L cosθ+γ SL ...Equation (1) Where, γ S To separate the surface tension of the functional layer, γ L γ is the surface tension of water. SLTo separate the interfacial tension of the functional layer and water. The angle θ formed by the tangent of water and the surface of the functional layer when satisfying the above formula (1) is the static contact angle of water. Note that since the static contact angle gradually changes to a smaller value over time, the value after 10 seconds from the water droplet falling on the surface of the functional layer is taken as the static contact angle of water.

[0059] (1-1-2) Characteristics (i) Proportion of macro-pores In the case of the functional layer of the composite semipermeable membrane according to the first embodiment, when the cross section in the thickness direction (cross section perpendicular to the first surface) observed by a scanning transmission electron microscope (hereinafter referred to as "STEM") is bisected into a region a on the first surface side and a region b on the second surface side, and the proportion of macro-pores having a pore diameter of 0.7 nm or more in the region a is set as A, and the proportion of macro-pores having a pore diameter of 0.7 nm or more in the region b is set as B, A / B is 1.40 or less. Hereinafter, the proportion of macro-pores having a pore diameter of 0.7 nm or more in the region a, A, and the proportion of macro-pores having a pore diameter of 0.7 nm or more in the region b, B, are also simply referred to as A and B, respectively.

[0060] In the case of the functional layer in which the cross-linked polyamide formed by interfacial polycondensation is the main component, there are pores in which water molecules or solute molecules can permeate between polyamide chains and within the structure of the polyamide network. If pores having a pore diameter of 0.7 nm or more are defined as macro-pores, a high proportion of macro-pores in the region means that the functional layer is a loose structure. If the functional layer is a loose structure, the water permeation resistance becomes low, but the solute removal performance also becomes low. On the other hand, a low proportion of macro-pores in the region means that the functional layer is a dense structure. If the functional layer is a dense structure, the water permeation resistance becomes high, but the solute removal performance improves.

[0061] The inventors of the present application have found that in the functional layer satisfying A / B of 1.40 or less, both a particularly high permeated water amount and a neutral molecule removal property can be achieved. From the viewpoint of achieving both the permeated water amount and the neutral molecule removal property, A / B is preferably 0.10 or more and 1.40 or less, more preferably 0.80 or more and 1.35 or less, further preferably 1.00 or more and 1.30 or less, and particularly preferably 1.10 or more and 1.30 or less.

[0062] A / B can be controlled by, for example, the type of water layer additive having an amide group or a urea group and monofunctional amine contained in the aqueous solution of polyfunctional amine, the concentration, the ratio of the concentration of monofunctional amine to the concentration of polyfunctional amine, the water fraction contained in the organic solvent in which the polyfunctional acid halide is dissolved, the coating amount of the polyfunctional acid chloride solution with respect to the surface area of the porous support layer, and the like, as described in the "Formation process of the functional layer" below.

[0063] The composite semipermeable membrane according to the present embodiment preferably has a ratio A of the proportion of the macrovoids in the region a of 0.10 or less. In the composite semipermeable membrane in which the proportion of the macrovoids near the surface of the separation functional layer is small, that is, the composite semipermeable membrane in which the value of A is small, the polyamide structure is dense to the extent suitable for removing solutes, and the removal performance of the composite semipermeable membrane is improved. From the viewpoint of simultaneously achieving the removal performance and the permeated water amount of the composite semipermeable membrane, A is more preferably 0.01 or more and 0.10 or less, and further preferably 0.03 or more and 0.08 or less.

[0064] In addition, in the composite semipermeable membrane in which the proportion of the macrovoids on the inner side of the separation functional layer is large, that is, the composite semipermeable membrane in which the value of B, the proportion of the macrovoids in the region b, is large, the polyamide structure is loose to the extent suitable for reducing the water permeation resistance, and the permeated water amount of the composite semipermeable membrane is improved. On the other hand, from the viewpoint of maintaining the physical strength of the separation functional layer, B is preferably 0.01 or more and 0.20 or less, more preferably 0.03 or more and 0.18 or less, and further preferably 0.05 or more and 0.15 or less.

[0065] A and B can be controlled by, for example, the kind of the water layer additive having an amide group or a urea group and the monofunctional amine contained in the aqueous solution of the polyfunctional amine, the concentration, the water content ratio in the organic solvent in which the polyfunctional acid halide is dissolved, the ratio of the concentration of the aliphatic amine to the concentration of the aromatic amine, and the like as described in the "Formation process of the separation functional layer" described later.

[0066] The proportion of the macrovoids is calculated by the method described in the "Proportion of macrovoids" of the Examples described later.

[0067] (ii) Carboxyl density In the composite semipermeable membrane according to the second embodiment, the ratio Nd / Nf of the carboxyl densities determined by STEM in the cross section in the thickness direction of the separation functional layer (the cross section perpendicular to the first surface) is 2.1 or less. Here, "Nd" refers to the carboxyl density of the region d, and "Nf" refers to the carboxyl density of the region f. The regions d and f refer to two regions among the regions c to g obtained by equally dividing the cross section in the thickness direction of the separation functional layer as shown in Figure 6

[0068] The separation functional layer having the crosslinked polyamide formed by the interfacial polycondensation as the main component has an amino group and a carboxyl group as the terminal functional groups. In the region in which the carboxyl density is high, the separation functional layer becomes a loose structure. If the separation functional layer is a loose structure, the water permeation resistance becomes low, but the removal performance of solutes also becomes low. On the other hand, in the region in which the carboxyl density is low, the separation functional layer becomes a dense structure. If the separation functional layer is a dense structure, the water permeation resistance becomes high, but the removal performance of solutes is improved. ​

[0069] Therefore, by making the separation functional layer have a gradient structure in which the ratio Nd / Nf of the carboxyl densities is 2.1 or less, both a particularly high permeated water amount and a neutral molecule removal performance can be achieved. From the viewpoint of achieving both the permeated water amount and the removal performance, Nd / Nf is preferably 0.1 or more and 1.9 or less, and more preferably 0.2 or more and 1.7 or less.

[0070] Nd / Nf can be controlled by, for example, the kind of the water layer additive having an amide group or a urea group and the monofunctional amine included in the aqueous solution of the polyfunctional amine, the concentration, the ratio of the concentration of the monofunctional amine to the concentration of the polyfunctional amine, the kind of the polyfunctional acid halide, the concentration, the water content ratio included in the organic solvent in which the polyfunctional acid halide is dissolved, the coating amount of the polyfunctional acid chloride solution with respect to the surface area of the porous support layer, and the like as described in the "Formation process of the separation functional layer" described later.

[0071] The carboxyl density of each region is calculated by the method described in the "Carboxyl density" of the Examples described later.

[0072] The composite semipermeable membrane according to the second embodiment preferably has Nd of 2.3 x 10 -26 mol / nm 2 and Nf of 0.7 x 10 -26 mol / nm 2 or more. For a membrane in which the carboxyl density near the surface layer is small, from the viewpoint that the polyamide structure is dense to the extent that is suitable for removing solutes, the removal performance of the membrane is improved, and the viewpoint of ensuring the permeated water amount of the membrane, Nd is more preferably 0.5 x 10 -26 mol / nm 2 or more and 2.1 x 10 -26 mol / nm 2 or less. Further preferably, Nd is 1.0 x 10 -26 mol / nm 2 or more and 1.6 x 10 -26 mol / nm 2 or less.

[0073] For a membrane in which the carboxyl density on the inner layer side of the separation functional layer is large, from the viewpoint that the polyamide structure is loose to the extent that is suitable for reducing the water permeation resistance, the permeated water amount of the membrane is improved, and the viewpoint of maintaining the physical strength of the functional layer, Nf is more preferably 0.9 x 10 -26 mol / nm 2 or more and 2.5 x 10 -26 mol / nm 2 or less. Further preferably, Nf is 1.0 x 10 -26 mol / nm 2 or more and 2.0 x 10 -26mol / nm 2 The following.

[0074] The amounts of the terminal amino groups C, the terminal carboxyl groups D, and the amide groups E of the crosslinked polyamide can be controlled by, for example, the kind and the concentration of the water layer additive contained in the multifunctional amine solution and the monofunctional amine, the kind and the concentration of the multifunctional acyl halide, the water content rate contained in the organic solvent in which the multifunctional acyl halide is dissolved, the coating amount of the multifunctional acyl chloride solution with respect to the surface area of the porous support layer, and the like as described later in the "Process for forming a separation functional layer".

[0075] (iii) the amount C of the terminal amino groups, the amount D of the terminal carboxyl groups, and the amount E of the amide groups of the crosslinked polyamide When the amount C of the terminal amino groups, the amount D of the terminal carboxyl groups and the amount E of the amide groups of the crosslinked polyamide in the separation functional layer are set to C, D and E respectively, E / (C+D) is preferably 1.7 or more in the composite semipermeable membrane according to the present embodiment. Here, "E / (C+D)" means the ratio of the amount of the amide groups of the crosslinked polyamide contained in the separation functional layer with respect to the amount of the terminal groups.

[0076] By making the amount of the amide groups as the crosslinking points relatively larger than the sum of the amounts of the terminal amino groups and the terminal carboxyl groups, the compactness of the separation functional layer is improved, and the solute removal property and the chemical and physical strength of the separation functional layer are improved. From the above viewpoint and the viewpoint of ensuring the permeated water amount, E / (C+D) is more preferably 1.8 or more and 2.2 or less, and further preferably 1.9 or more and 2.1 or less.

[0077] The amounts C, D and E of the terminal amino groups, the terminal carboxyl groups and the amide groups of the crosslinked polyamide can be controlled by, for example, the concentration of the multifunctional amine and the multifunctional acyl halide as the monomers, the polymerization time, and the like. 13 The amounts C, D and E of the terminal amino groups, the terminal carboxyl 13 groups and the amide groups of the crosslinked polyamide can be calculated from the C solid-state nuclear magnetic resonance measurement (hereinafter referred to as "C solid-state NMR measurement"). Specifically, after the substrate is peeled from the composite semipermeable membrane to obtain the separation functional layer and the porous support layer, the porous support layer is removed by dissolving it, and the separation functional layer is obtained. The obtained separation functional layer is subjected to the C solid-state NMR measurement based on the DD / MAS method, and each ratio is calculated from the comparison of the integral values of the carbon peaks of each functional group or the carbon peaks bonded to each functional group. 13

[0078] The amounts C, D and E of the terminal amino groups, the terminal carboxyl and the amide groups of the crosslinked polyamide can be controlled by, for example, concentrations of the multifunctional amine and the multifunctional acyl halide as the monomer, polymerization time, and the like.

[0079] (iv) separation properties The composite semipermeable membrane according to the present embodiment is suitable for the separation of nonionic solutes in addition to ionic solutes such as sodium chloride, and has a feature in the difference in the solute removal property of each solute.

[0080] ​The silica removal rate when raw water containing 500 ppm of sodium chloride (hereinafter referred to as "NaCl"), 20 ppm of silica as a non-ionic neutral molecule, and 1 ppm of boron is made to pass through the composite semipermeable membrane according to the present embodiment at an operating pressure of 0.75 MPa is preferably 99.30% or more, more preferably 99.45% or more. In addition, the boron removal rate of the composite semipermeable membrane is preferably 60% or more, more preferably 65% or more, and further preferably 70% or more. Furthermore, the NaCl removal rate of the composite semipermeable membrane is preferably 99.50% or more, more preferably 99.60% or more, and on the other hand, is preferably less than 99.90%. In addition, the difference between the silica removal rate and the NaCl removal rate is preferably 0.20% or less.

[0081] If the silica removal rate, the boron removal rate, the NaCl removal rate, and the difference between the silica removal rate and the NaCl removal rate are within the above ranges, permeated water of high water quality can be obtained, and the inhibition of solute concentration on the membrane surface such as scale can be taken into account.

[0082] In addition, from the viewpoint of reducing the consumed energy when the raw water is treated with the composite semipermeable membrane, the permeated water amount under the above conditions is preferably 0.70 m 3 / day or more. 2

[0083] (1-2) Porous support layer The porous support layer is a support that forms the separation functional layer, and does not itself have separation performance of ions and the like.

[0084] As the size and distribution of the pores in the porous support layer, for example, a porous support layer having uniform and fine pores or fine pores that gradually increase from the surface on the side on which the separation functional layer is formed to the other surface, and the size of the fine pores in the surface on the side on which the separation functional layer is formed is 0.1 nm or more and 100 nm or less is preferred.

[0085] As for the porous support layer, for example, it can be obtained by casting a high-molecular polymer on a cloth, i.e., a base material, formed of at least one selected from the group consisting of a polyester and an aromatic polyamide. The composite semipermeable membrane according to the present embodiment can have only the porous support layer and the separation functional layer, as shown in Figure 1 Note that, hereinafter, for the configuration in which the porous support layer is formed on the base material, it is sometimes referred to as a "supporting membrane".

[0086] ​As the raw material of the porous support layer, a homopolymer or copolymer of, for example, polysulfone, polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenyl sulfone, polyphenylene ether, or the like can be used alone or in combination. As the cellulose-based polymer, cellulose acetate, cellulose nitrate, or the like can be used, and as the vinyl polymer, polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, or the like can be used. Among these, as the raw material of the porous support layer, a homopolymer or copolymer of polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenyl sulfide, or the like is preferable, and cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenyl sulfone is more preferable. Among these raw materials, polysulfone is further preferable in terms of high chemical stability, mechanical stability, thermal stability, and ease of molding.

[0087] For example, a solution obtained by dissolving polysulfone in N,N-dimethylformamide (hereinafter referred to as "DMF") is cast on a dense polyester cloth or polyester nonwoven fabric to a certain thickness and is wet coagulated in water, whereby a support film having a surface in which a majority of the pores have a diameter of several tens of nm or less can be obtained.

[0088] The thickness of the support film described above affects the strength of the resulting composite semipermeable membrane and the packing density when the same is formed into an element. From the viewpoint of obtaining sufficient mechanical strength and packing density, the thickness of the support film is preferably 30 μm or more and 300 μm or less, and more preferably 100 μm or more and 220 μm or less.

[0089] The morphology of the porous support layer can be observed by a scanning electron microscope, a transmission electron microscope, or an atomic force microscope. For example, in the case of observation with a scanning electron microscope, the porous support layer peeled from the substrate is cut with a freeze-fracture method, and the resulting sample is observed as a cross section. A thin layer of platinum, platinum-palladium, or ruthenium tetrachloride is applied to the sample, and observation is performed at an acceleration voltage of 3 to 15 kV by a high-resolution field emission scanning electron microscope (hereinafter referred to as "UHR-FE-SEM"). As the UHR-FE-SEM, an S-900 electron microscope manufactured by Hitachi, Ltd., or the like can be used.

[0090] The thickness of the porous support layer in the composite semipermeable membrane according to the present embodiment is preferably 20 μm or more and 100 μm or less. If the thickness of the porous support layer is 20 μm or more, good pressure resistance can be obtained, and a uniform support film free from defects can be obtained. The composite semipermeable membrane having such a porous support layer exhibits good desalination performance. In addition, if the thickness of the porous support layer is 100 μm or less, the amount of unreacted substances remaining at the time of production can be reduced, and a decrease in the amount of permeated water and a decrease in chemical resistance can be suppressed.

[0091] (2) Production method (2-1) Formation process of the porous support layer The formation process of the porous support layer includes a process of applying a polymer solution on a substrate and a process of immersing the above substrate on which the solution is applied in a coagulation bath to coagulate the polymer.

[0092] In the process of applying the polymer solution on the substrate, the polymer solution is prepared by dissolving a polymer that is a component of the porous support layer in a good solvent for the polymer.

[0093] As for the temperature of the polymer solution at the time of applying the polymer solution, for example, when using a polysulfone as the polymer, it is preferably 10°C or higher and 60°C or lower. If the temperature of the polymer solution is within the above range, the polymer does not precipitate, and the polymer solution is sufficiently impregnated between the fibers of the substrate and then solidified. As a result, by the anchoring effect, the porous support layer is firmly joined to the substrate, and a good support membrane can be obtained. Note that the preferable temperature range of the polymer solution can be appropriately adjusted depending on the kind of the polymer used, the desired viscosity of the solution, and the like.

[0094] The time from when the polymer solution is applied on the substrate until it is immersed in the coagulation bath is preferably 0.1 seconds or longer and 5 seconds or shorter. If the time until the immersion in the coagulation bath is within the above range, the organic solvent solution containing the polymer is sufficiently impregnated between the fibers of the substrate and then solidified. Note that the preferable range of the time until the immersion in the coagulation bath can be appropriately adjusted depending on the kind of the polymer solution used, the desired viscosity of the solution, and the like.

[0095] As the coagulation bath, water is generally used, but there is no particular limitation as long as the polymer that is a component of the porous support layer is not dissolved. Depending on the composition of the coagulation bath, the morphology of the obtained porous support layer changes, and the composite semipermeable membrane obtained thereby also changes. The temperature of the coagulation bath is preferably -20°C or higher and 100°C or lower, and more preferably 10°C or higher and 50°C or lower. If the temperature of the coagulation bath is within the above range, the vibration of the surface of the coagulation bath due to thermal motion does not become intense, and the smoothness of the surface of the porous support layer after the formation of the porous support layer is maintained. In addition, if the temperature is within the above range, the coagulation speed is appropriate, and the film formation properties become good.

[0096] Next, the obtained support membrane is subjected to a hot water washing in order to remove the solvent remaining in the membrane. The temperature of the hot water is preferably 40°C or higher and 100°C or lower, and more preferably 60°C or higher and 95°C or lower. If the temperature of the hot water is within the above range, the shrinkage of the support membrane does not become large, and the permeation water amount becomes good. In addition, if the temperature of the hot water is within the above range, a sufficient washing effect can be obtained.

[0097] (2-2) Formation process of the separation function layer In the production method of the composite semipermeable membrane according to the present embodiment, the separation functional layer is formed by interfacial polycondensation of a polyfunctional amine aqueous solution and a polyfunctional acid halide solution on the porous support layer. The polyfunctional amine aqueous solution contains a polyfunctional amine, a monofunctional amine having a molecular weight of 150 or less, and a water layer additive having an amide group or a urea group. The polyfunctional acid halide solution contains a polyfunctional acid halide and an organic solvent.

[0098] The preferred embodiments of the polyfunctional amine and the polyfunctional acid halide are the same as described above. Hereinafter, the process will be described using, for example, a polyfunctional aromatic amine as the polyfunctional amine and a polyfunctional aromatic acid chloride as the polyfunctional acid halide.

[0099] As the organic solvent that dissolves the polyfunctional aromatic acid chloride, any organic solvent that is immiscible with water, does not damage the support membrane, and does not hinder the generation reaction of the crosslinked aromatic polyamide can be used. As representative examples of the organic solvent that dissolves the polyfunctional aromatic acid chloride, liquid hydrocarbons, halogenated hydrocarbons such as trichlorotrifluoroethane can be given. From the viewpoint of being a substance that does not damage the ozone layer, ease of obtaining, ease of handling, and safety in handling, it is preferable to use a single substance such as octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane, cyclooctane, ethylcyclohexane, 1-octene, 1-decene, or a mixture thereof.

[0100] In the production method of the composite semipermeable membrane according to the present embodiment, the moisture content in the organic solvent that dissolves the polyfunctional acid halide is preferably 10 ppm or more and 50 ppm or less. By reducing the moisture in the organic solvent, the polycondensation reaction of the polyfunctional amine and the polyfunctional acid halide can be inhibited, and an appropriate surface pore diameter can be formed. In addition, if the moisture content in the organic solvent that dissolves the polyfunctional acid halide is 50 ppm or less, the inhibition of the polycondensation reaction is suppressed, and the density of the surface layer of the separation functional layer can be highly maintained. As a result, a separation functional layer in which the proportion A of the coarse pores in the vicinity of the surface layer is small and the proportion B of the coarse pores on the inner layer side is large, or a separation functional layer in which the carboxyl group in the vicinity of the surface layer is reduced and Nd / Nf is small, can be easily manufactured. For the above reasons, the moisture content in the organic solvent that dissolves the polyfunctional acid halide is more preferably 10 ppm or more and 30 ppm or less.

[0101] The moisture content in the organic solvent can be measured by Karl Fischer titration method described in JIS K0068:2001. The Karl Fischer method includes volumetric titration method or coulometric titration method, and in the present specification, the coulometric titration method is used.

[0102] In the production method of the composite semipermeable membrane according to the present embodiment, the aqueous polyfunctional amine solution contains a polyfunctional amine, a monofunctional amine having a molecular weight of 150 or less, and a water layer additive having an amide group or a urea group. By the presence of the monofunctional amine having a molecular weight of 150 or less in the interfacial polycondensation, the monofunctional amine diffuses into the polyamide network and reacts with the terminal carboxyl group of the surface layer portion, whereby the proportion A of the coarse pores in the vicinity of the surface layer of the separation functional layer can be reduced, or the carboxyl group in the vicinity of the surface layer of the separation functional layer can be reduced. From the viewpoint of being able to sufficiently diffuse into the polyamide network, the molecular weight of the monofunctional amine is preferably 120 or less, more preferably 100 or less, and further preferably 50 or less.

[0103] In the production method of the composite semipermeable membrane according to the present embodiment, the concentration of the monofunctional amine having a molecular weight of 150 or less in the aqueous polyfunctional amine solution is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.05% by mass or more and 8% by mass or less. If the concentration of the monofunctional amine is within the above range, the removal of neutral molecules can be improved without impairing the desalination performance of the separation functional layer.

[0104] In addition, by the presence of the water layer additive having an amide group or a urea group in the aqueous polyfunctional amine solution, the hydrolysis reaction of the acid chloride with water is promoted on the side of the separation functional layer in the vicinity of the interface, and the proportion B of the coarse pores of the inner layer portion of the separation functional layer can be increased, or the carboxyl group density of the inner layer portion can be increased as compared with the surface layer portion.

[0105] As the water layer additive having an amide group, for example, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N-methylpyrrolidone, γ-butyrolactam, ε-caprolactam, and the like can be given.

[0106] As the water layer additive having a urea group, for example, urea, dimethylurea, diethylurea, dibutylurea, diphenylurea, tetramethylurea, tetraethylurea, bis(pentamethylene)urea, 2-imidazolidone, 1,3-dimethyl-2-imidazolidone, dimethyloxymethylurea, diethyloxymethylurea, N,N-dimethylpropyleneurea, N,N'-dimethylolurea, dimethylol ethylene urea, dimethylol dihydroxy ethylene urea, dimethylol propylene urea, tetramethylol acetylene diurea, and the like can be given.

[0107] In the production method of the composite semipermeable membrane according to the present embodiment, in the aqueous polyfunctional amine solution, the concentration of the water layer additive is preferably 0.1% by mass or more and 10% or less, and more preferably 0.5% by mass or more and 5% by mass or less. If the concentration of the water layer additive in the aqueous polyfunctional amine solution is within the above range, a separation functional layer that ensures the separation performance and the mechanical strength can be formed while sufficiently promoting the hydrolysis reaction inside the functional layer.

[0108] In order to perform the interfacial polycondensation on the porous support layer, first, the surface of the porous support layer is coated with the aqueous solution of the polyfunctional aromatic amine. The concentration of the polyfunctional aromatic amine in the aqueous solution is preferably 0.1 mass% or more and 20 mass% or less, and more preferably 0.5 mass% or more and 15 mass% or less.

[0109] As the method of coating the surface of the porous support layer with the aqueous solution of the polyfunctional aromatic amine, known coating means such as a method of applying the aqueous solution to the surface of the porous support layer, a method of immersing the porous support layer in the aqueous solution, and the like can be mentioned, as long as the surface of the porous support layer is uniformly and continuously coated with the aqueous solution.

[0110] The contact time of the porous support layer with the aqueous solution of the polyfunctional aromatic amine is preferably 5 seconds or more and 10 minutes or less, and more preferably 10 seconds or more and 3 minutes or less. Subsequently, it is preferable to remove the excess applied aqueous solution by a liquid removal process. As the method of removing the liquid, a method of holding the support film surface in the vertical direction and allowing it to naturally flow down, and the like can be mentioned. After the liquid removal, the surface of the support film is dried, and it is possible to remove all or a part of the water of the aqueous solution.

[0111] Then, the above-mentioned solution of the polyfunctional aromatic acid chloride is applied to the porous support layer which has been coated with the aqueous solution of the polyfunctional aromatic amine, and a crosslinked aromatic polyamide is formed by interfacial polycondensation. The time of performing the interfacial polycondensation is preferably 0.1 seconds or more and 3 minutes or less, and more preferably 0.1 seconds or more and 1 minute or less.

[0112] From the viewpoint of sufficiently forming the separation function layer and the viewpoint of cost, the concentration of the polyfunctional aromatic acid chloride in the solution of the polyfunctional aromatic acid chloride is preferably 0.01 mass% or more and 1.0 mass% or less.

[0113] Subsequently, it is preferable to remove the organic solvent remaining after the reaction by a liquid removal process. As the removal of the organic solvent, a method of holding the composite semipermeable membrane in the vertical direction and removing the excess organic solvent by allowing it to naturally flow down can be employed, for example. In this case, the time of holding in the vertical direction is preferably 1 minute or more and 5 minutes or less, and more preferably 1 minute or more and 3 minutes or less. If the holding time is 1 minute or more, it is easy to obtain a crosslinked aromatic polyamide having a target function, and if it is 5 minutes or less, it is possible to suppress the generation of defects due to the excessive drying of the organic solvent, and thus it is possible to suppress the decrease in performance.

[0114] (3) Use of the composite semipermeable membrane The composite semipermeable membrane according to the present embodiment is wound around a cylindrical water collecting pipe provided with a plurality of holes together with a raw water flow path material such as a plastic net and a permeated water flow path material such as a tricot, and a membrane for improving pressure resistance as needed, and can be used as a spiral-type composite semipermeable membrane element. In addition, the element can be connected in series or in parallel and housed in a pressure container to produce a composite semipermeable membrane assembly.

[0115] In addition, the composite semipermeable membrane, the element, and the assembly described above can be combined with a pump for supplying raw water thereto, a device for pretreating the raw water, and the like, thereby constituting a fluid separation device. By using the separation device, it is possible to separate raw water into permeated water such as drinking water and concentrated water that does not permeate the membrane, thereby obtaining water that meets the purpose.

[0116] From the viewpoint of improving the desalination rate and the membrane permeation flux, the temperature of the raw water supplied to the fluid separation device is preferably 5°C or higher and 45°C or lower. In addition, in order to suppress the generation of scale such as magnesium and to suppress the deterioration of the membrane, it is preferable to operate with the pH of the raw water in the neutral range.

[0117] The assembly using the composite semipermeable membrane according to the present embodiment is characterized by high removal of neutral molecules. For example, in the case of manufacturing ultrapure water from raw water containing extremely small amounts of organic matter and silicates in an ultrapure water manufacturing process for manufacturing semiconductors, it is particularly suitable to be introduced into the process.

[0118] (3-1) Method for manufacturing ultrapure water As shown in Figure 7 The method for manufacturing ultrapure water described below includes a pretreatment step of removing suspended substances from raw water, a first treatment step (reverse osmosis step) of removing silicon dioxide using a reverse osmosis membrane from the aqueous solution after the pretreatment step, and a second treatment step of removing ionic components from the aqueous solution after the step of using a reverse osmosis membrane.

[0119] Note that it is necessary for the method for manufacturing ultrapure water according to the present embodiment to perform only the reverse osmosis step, and the other steps are optional steps. Hereinafter, each of the steps will be described.

[0120] (3-2) Pretreatment step (3-2-1) Raw water The raw water targeted in the present embodiment is an aqueous solution containing silica (hereinafter, referred to as "aqueous solution containing silica" regardless of before or after the implementation of the pretreatment step), and specifically, for example, river water, underground water, waste water recovery water, cooling water backflow water, and the like can be given. Silica is present in the form of silicate, and the charged state changes depending on the pH of the raw water, but is not easily charged in the neutral range (pH 6 to 8). In addition, boric acid also changes the charged state depending on the pH of the raw water, but is not easily charged in the neutral range (pH 6 to 8).

[0121] (3-2-2) Pretreatment method The ultrapure water production method of the present embodiment preferably includes a pretreatment step of removing suspended substances in the raw water before the subsequent primary treatment step (reverse osmosis step). The suspended substances contained in the raw water cause clogging (fouling) when adhering to the surface of the reverse osmosis membrane used in the subsequent primary treatment step, and thus by filtering a part or all of the raw water through an MF membrane (microfiltration membrane) or an UF membrane (ultrafiltration membrane) (pretreatment) and then supplying it to the primary treatment step, it is possible to suppress fouling.

[0122] (3-3) Primary treatment step (reverse osmosis step) (3-3-1) Reverse osmosis membrane (RO membrane) The ultrapure water production method of the present embodiment includes a reverse osmosis step of removing silica from an aqueous solution containing silica using the composite semipermeable membrane of the present embodiment. That is, the ultrapure water production method of the present embodiment includes a step of using the composite semipermeable membrane of the present embodiment as a reverse osmosis membrane in the primary treatment step to separate and remove silica from the raw water or the aqueous solution treated by the pretreatment step. Since the reverse osmosis membrane has a high permeate water amount, it is possible to operate at a high recovery rate without increasing the operating pressure to reduce the amount of concentrated water (reject water), and a high-efficiency process can be achieved. In addition, since the reverse osmosis membrane has a high silica removal rate, it is possible to reduce the silica concentration of the aqueous solution supplied from the primary treatment step to the subsequent secondary treatment step. Therefore, it is possible to suppress the precipitation of silica on the surface of the ion exchange resin used in the secondary treatment step, and the reduction in the treatment efficiency of the secondary treatment step and the deterioration of the ion exchange resin caused thereby.

[0123] (3-3-2) Operation method The filtration using the reverse osmosis membrane is preferably performed at a pressure of 0.10 MPa or more and 12 MPa or less. If the pressure is 0.10 MPa or more, the decrease in the membrane permeation rate of water can be suppressed, and if the pressure is 12 MPa or less, the possibility of damage to the membrane can be reduced. From the above viewpoint, the pressure at which the raw water or the water solution after the pretreatment is supplied is more preferably 0.25 MPa or more and 6 MPa or less, and further preferably 0.25 MPa or more and 1 MPa or less. The permeated water amount of the reverse osmosis membrane is 0.85 m 3 / m 2 / day or more, a sufficient permeated water amount can be obtained even in low-pressure operation of 1 MPa or less, the energy consumption per water production amount and the water production cost can be reduced, and a device design based on a small-scale pump can be performed, and thus the space can be saved.

[0124] The one-time treatment step can be a multistage treatment, that is, the water solution after the pretreatment can be filtered through a first reverse osmosis membrane, and the obtained permeated water can be treated through a second reverse osmosis membrane. Alternatively, in order to reduce the discarded water and improve the recovery rate, the concentrated water obtained by filtering through the first reverse osmosis membrane can be treated through the second reverse osmosis membrane.

[0125] (3-4) Two-time treatment step The ultrapure water production method of the present embodiment preferably further includes a step of removing solute salts from the water solution treated through the reverse osmosis step using an ion exchange resin. That is, a two-time treatment step of further removing ionic components from the permeated water obtained through the one-time treatment step to produce ultrapure water is preferably included. The two-time treatment step preferably uses an ion exchange resin (hereinafter also referred to as "ion exchanger").

[0126] As the method using the ion exchange resin, an ion exchange device including a cation exchange resin and an anion exchange resin can be used, or an electrically regenerative deionization (hereinafter referred to as "EDI") can be used. The EDI is a device having a desalination chamber filled with an ion exchanger divided by an ion exchange membrane, a concentration chamber that concentrates ions that have been desalinated using the desalination chamber, and an anode and a cathode for passing an electric current, and is a device that simultaneously performs desalination (deionization) treatment of the treated water using the ion exchanger and regeneration treatment of the ion exchanger by passing an electric current to operate. The treated water passed into the EDI is desalinated by the ion exchanger filled in the desalination chamber, and is discharged to the outside of the EDI as EDI-treated water. Similarly, the concentrated water in which ions are concentrated is discharged to the outside as EDI-concentrated water.

[0127] Further, as the two-time treatment step, UV treatment can be included.

[0128] Example The present application will be described below by using examples, but the present application is not limited by any of these examples.

[0129] <Water content of organic solvent> The water content of the organic solvent before dissolving the polyfunctional acyl halide was measured by Karl Fischer method coulometric titration using a moisture meter (CA-200 manufactured by Mitsubishi Chemical Analytech).

[0130] <Removal rate of solute> Membrane filtration treatment was performed by supplying raw water having a temperature of 25°C, a pH of 7, adjusted to 500 ppm of sodium chloride, 87 ppm of sodium metasilicate (20 ppm as silicon dioxide), and 5.7 ppm of boric acid (1 ppm as boron) to the composite semipermeable membrane at an operating pressure of 0.75 MPa. The membrane area of the composite semipermeable membrane was set to 33 cm 2 After 2 hours from the start of the membrane filtration treatment, the permeated water was sampled for 20 minutes. The conductivities of the raw water and the permeated water were measured with a conductivity meter (CM-41X manufactured by Toa Electronics Ltd.), and the respective practical salinities, i.e., NaCl concentrations, were obtained. The NaCl removal rate was calculated from the obtained NaCl concentrations based on the following equation. Here, the NaCl concentration (ppm) refers to the concentration on a mass basis.

[0131] NaCl removal rate (%) = 100 x {1 - (NaCl concentration in permeated water / NaCl concentration in raw water)} In addition, the silicon dioxide concentration and the boron concentration of the raw water and the permeated water were measured by an ICP emission analysis device (5110 VDV manufactured by Agilent), and the silicon dioxide removal rate and the boron removal rate were calculated from the following equations.

[0132] Silicon dioxide removal rate (%) = 100 x {1 - (silicon dioxide concentration in permeated water / silicon dioxide concentration in raw water)} Boron removal rate (%) = 100 x {1 - (boron concentration in permeated water / boron concentration in raw water)} <Permeated water amount> In the test of the "removal rate of solute" described above, the membrane permeated water amount of the raw water was measured, and the value converted to the permeated water amount (cubic meters) per 1 square meter of membrane surface per day was taken as the permeated water amount (m 3 / m 2 / day).

[0133] <Proportion of coarse pores> A 5cm square composite semi-permeable membrane, obtained by physically peeling off the substrate, was processed using a cryo-ultrathroplasty method, placed on a copper grid, and immersed in pure water for 4 hours, followed by immersion in a 10% (w / w) 2-propanol aqueous solution for 1 hour, and then washed. After removing the moisture from the sample with filter paper, it was freeze-dried to obtain the sample for measurement. The prepared sample was imaged using a field emission transmission electron microscope (Hitachi High-Tech HF5000) at an accelerating voltage of 200kV, obtaining STEM images at 100,000x magnification. The images were then analyzed using image processing software, such as... Figure 5 As shown, in each protrusion of the pleated structure of the separation functional layer, within a random region encompassing 50-100% of its height, a reference point P is determined on the outer surface 26 of the separation functional layer (facing the side opposite to the porous support layer). Centered on the normal V0 passing through reference point P, straight lines V1 and V2, parallel to the normal V0, are drawn on both sides at intervals of 3-10 nm. Additionally, a tangent Z1 is drawn on the outer surface of the separation functional layer passing through reference point P, and a tangent Z2 is drawn on the inner surface 25 of the separation functional layer (the side contacting the porous support layer), parallel to it. Between Z1 and Z2, a straight line Z3 is drawn that bisects the interval between Z1 and Z2. The regions surrounded by V1 and V2 and enclosed by Z1, Z2, and the line Z3 between them are sequentially designated as region a and region b, starting from the outer surface side of the separation functional layer. The areas of region a and region b are set to 10 nm. 2 Above 80nm 2 Next, DeConvHAADF (HREM research inc.) was used to deconvolve the STEM image to emphasize the structure of the pores and polyamide. Then, ImageJ was used for binarization and particle size analysis to quantitatively analyze the number and diameter of pores in each region. Through this analysis, the pore diameter and area were calculated for each pore in terms of the number of pixels in the image. For the calculated pore diameter and area, the proportions A and B of coarse pores with a diameter greater than 0.7 nm in regions a and b were calculated according to the following formulas. It should be noted that the average proportion of coarse pores obtained for the five protrusions of the separated functional layer was used as the proportion of coarse pores in each region.

[0134] The proportion of large holes, A = the total number of pixels with large holes in region a / the total number of pixels with all holes in region a. The proportion of large holes, B = the total number of pixels with large holes in region b / the total number of pixels with all holes in region b. <Carboxyl group density> A 5cm square composite semi-permeable membrane, obtained by physically peeling off the substrate, was processed using a cryo-ultrathroplasty method, placed on a copper grid, and immersed in pure water for 4 hours, followed by immersion in a 10% (w / w) 2-propanol aqueous solution for 1 hour, and then washed. Then, the sample was subjected to a total of 3 times of treatment at a pH adjusted to 3.8 and 25°C using a 1.0 × 10⁻⁶ ppm solution. -3 The sample was immersed in a mol / L barium chloride aqueous solution for 10 minutes, followed by a total of 4 times of immersion in a 1.0×10⁻⁶ solution adjusted to pH 3.8 and 25°C. -7 The sample was immersed in a mol / L barium chloride aqueous solution for 7 minutes. Then, the moisture was removed with filter paper, and the sample was freeze-dried to obtain the test sample. The prepared test sample was imaged using a field emission transmission electron microscope (Hitachi High-Tech HF5000) at an accelerating voltage of 200 kV, obtaining a 100,000x STEM image. Then, as... Figure 6 As shown, in each protrusion of the pleated structure of the separation functional layer, within a random region encompassing 50-100% of its height, a reference point P is determined on the outer surface 26 of the separation functional layer (facing the side opposite to the porous support layer). Centered on the normal V0 passing through reference point P, straight lines V1 and V2, parallel to the normal V0, are drawn on both sides at intervals of 3-10 nm. Additionally, a tangent Z1 is drawn on the outer surface of the separation functional layer passing through reference point P, and a tangent Z2 is drawn on the inner surface 25 of the separation functional layer (the side contacting the porous support layer), parallel to it. Between Z1 and Z2, four straight lines dividing this interval into five equal parts are drawn. The regions surrounded by V1 and V2 and enclosed by Z1, Z2, and the lines between them are sequentially designated as regions c-g, starting from the first surface of the composite semipermeable membrane. The area of ​​each region c-g is set to 5 nm. 2 The above 30nm 2 The following steps are performed. The obtained images are analyzed using image processing software. For regions c to g, brightness is measured using STEM. Within the minimum brightness Lmin and maximum brightness Lmax of these measurements, the area of ​​regions exhibiting brightness greater than {Lmin + (Lmax - Lmin) / 3} is integrated for each region. This integrated value represents the total area of ​​portions containing carboxyl groups labeled with barium (Ba). The resulting integrated value is then divided by the area of ​​each carboxyl molecule (0.04 nm). 2 ), Avogadro's constant (6.0 × 10⁻⁶) 23 The carboxyl density (mol / nm) can be calculated from the number of groups per mol and the area of ​​each region. 2 It should be noted that the average carboxyl density measured at five protrusions of a randomly selected separation functional layer is taken as the carboxyl density of each region.

[0135] <Terminal amino group amount C, terminal carboxyl group amount D, amide group amount E> From composite semipermeable membrane 5m 2 The substrate was physically stripped to recover the porous support layer and the separation functional layer. After drying at 25°C for 24 hours, small amounts were added gradually to a beaker containing dichloromethane and stirred to dissolve the polymer constituting the porous support layer. The insoluble matter in the beaker was recovered using filter paper. This insoluble matter was then added to a beaker containing dichloromethane and stirred to recover the insoluble matter. This process was repeated until no further dissolution of the polymer forming the porous support layer into the dichloromethane solution was detected. The recovered separation functional layer was dried using a vacuum dryer to remove residual dichloromethane. The resulting separation functional layer was cryogenically pulverized to form a powder sample, which was then sealed in a sample tube for solid-state NMR analysis using CP / MAS and DD / MAS methods. 13 C10 solid-state NMR determination. 13 For the 1000 saturated solid NMR determination, a Chemagnetics CMX-300 was used. The determination conditions are shown below.

[0136] Standard substance: polydimethylsiloxane (internal standard: 1.56 ppm) Sample rotation speed: 10.5 kHz Pulse repetition time: 100s Based on the obtained spectrum, peaks originating from carbon atoms bonded to each functional group are segmented, and the functional group ratio is quantified based on the area of ​​the segmented peaks.

[0137] <Contact Angle> The static contact angle was automatically calculated using a Drop Master DM500 (manufactured by Kyowa Interface Science Co., Ltd.) via the θ / 2 method and computer image analysis. It should be noted that the droplet volume was set to 1.5 μl, and the static contact angle was measured 10 seconds after the distilled water was dropped onto the separation functional layer.

[0138] [Example 1] At 25°C, a polyester nonwoven fabric made of long fibers (air permeability 2.0 cc / cm²) was tested. 2A 15.0 mass% DMF solution of polysulfone was cast on a glass plate, immediately immersed in pure water and left for 5 minutes, thereby producing a support film having a porous support layer with a thickness of 40 μm. Next, after the support film was immersed in a multifunctional amine aqueous solution in which 2.0 mass% of m-PDA as a multifunctional amine, 0.1 mass% of ethylamine as a monofunctional amine having a molecular weight of 150 or less, and 1.2 mass% of DMF as a water layer additive were dissolved, the excess aqueous solution was removed. Further, using n-decane having a moisture content of 40 ppm as an organic solvent, a multifunctional acyl halide solution prepared so that the concentration of TMC as a multifunctional acyl halide was 0.10 mass% was coated at a rate of 300 mL / m 2 The surface of the porous support layer was completely wetted, and the separation function layer was formed by interfacial polycondensation. Next, in order to remove the excess solution from the film, the film was vertically placed to perform liquid removal, dried by blowing air at 25°C using an air blower, and washed with pure water at 80°C, thereby obtaining the composite semipermeable membrane of Example 1.

[0139] [Example 2] A composite semipermeable membrane of Example 2 was obtained by the same method as in Example 1, using ε-caprolactam (hereinafter referred to as "εCL") as a water layer additive.

[0140] [Example 3] A composite semipermeable membrane of Example 3 was obtained by the same method as in Example 1, using N,N'-dimethylpropylene urea (hereinafter referred to as "DMPU") as a water layer additive.

[0141] [Example 4] A composite semipermeable membrane of Example 4 was obtained by the same method as in Example 1, except that the concentration of ethylamine was set to 0.2 mass%.

[0142] [Example 5] A composite semipermeable membrane of Example 5 was obtained by the same method as in Example 1, using aniline as a monofunctional amine and tetramethyl urea (hereinafter referred to as "TMU") as a water layer additive.

[0143] [Example 6] A composite semipermeable membrane of Example 6 was obtained by the same method as in Example 1, using methylamine as a monofunctional amine and setting the concentration of DMF to 2.0 mass%.

[0144] [Example 7] A composite semipermeable membrane of Example 7 was obtained by the same method as in Example 1, using methylamine as a monofuctional amine and setting the moisture content of n-decane to 20 ppm.

[0145] [Example 8] The water content of n-decane was set to 80 ppm, and otherwise, the composite semipermeable membrane of Example 8 was obtained by the same method as in Example 7.

[0146] [Example 9] Heptylamine was used as the monofunctional amine, and otherwise, the composite semipermeable membrane of Example 9 was obtained by the same method as in Example 1.

[0147] [Comparative Example 1] Ethylamine and DMF were not added to the aqueous solution of the polyfunctional amine, and otherwise, the composite semipermeable membrane of Comparative Example 1 was obtained by the same method as in Example 1.

[0148] [Comparative Example 2] DMF was not added to the aqueous solution of the polyfunctional amine, and otherwise, the composite semipermeable membrane of Comparative Example 2 was obtained by the same method as in Example 1.

[0149] [Comparative Example 3] Ethylamine was not added to the aqueous solution of the polyfunctional amine, and otherwise, the composite semipermeable membrane of Comparative Example 3 was obtained by the same method as in Example 1.

[0150] [Comparative Example 4] Ethylamine was changed to 1,3,5-triaminobenzene (hereinafter referred to as "TAB") as the polyfunctional amine, and otherwise, the composite semipermeable membrane of Comparative Example 4 was obtained by the same method as in Example 1.

[0151] [Comparative Example 5] The concentration of m-PDA was changed to 3.0 mass%, and the concentration of TMC was changed to 0.165 mass%, and otherwise, the composite semipermeable membrane of Comparative Example 5 was obtained by the same method as in Comparative Example 1.

[0152] [Comparative Example 6] DMF was not added to the aqueous solution of the polyfunctional amine, and 0.10 mass% of DMF was added to the polyfunctional acid halide solution as an organic layer additive, and otherwise, the composite semipermeable membrane of Comparative Example 6 was obtained by the same method as in Example 1.

[0153] [Comparative Example 7] 1.2 mass% of εCL was added to the aqueous solution of the polyfunctional amine as a water layer additive, and 0.10 mass% of DMF was added to the polyfunctional acid halides solution as an organic layer additive, and otherwise, the composite semipermeable membrane of Comparative Example 7 was obtained by the same method as in Comparative Example 1.

[0154] The structures and properties of the composite semipermeable membranes obtained by Examples 1 to 9 and Comparative Examples 1 to 7 are shown in Table 1.

[0155] [Table 1] Thus, the composite semipermeable membrane of Examples 1 to 9 in which A / B is 1.40 or less or Nd / Nf is 2.1 or less achieves both a high permeate water amount and a neutral molecule removal property.

[0156] The above describes preferred embodiments of the present application, but the present application is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present application.

[0157] This application is based on Japanese Patent Application (Japanese Patent Application No. 2024-049332 filed on March 26, 2024) and Japanese Patent Application (Japanese Patent Application No. 2024-049342 filed on March 26, 2024), the contents of which are incorporated herein by reference in its entirety.

[0158] Explanation of Reference Numerals 1 composite semipermeable membrane 2 base material 3 porous support layer 4 separation function layer 11 first face of composite semipermeable membrane 12 second face of composite semipermeable membrane 21 protrusion i 22 protrusion ii 23 height of protrusion i 24 height of protrusion ii 25 inner surface of separation function layer 26 outer surface of separation function layer 27 wrinkle thickness X average line of roughness curve Yp1-5 elevation of hilltops from the highest hilltop to the fifth hilltop from X Yv1-5 elevation of valley bottoms from the lowest valley bottom to the fifth valley bottom from X L reference length P reference point V0 normal line passing through reference point P V1, V2 straight line parallel to normal line V0 Z1 tangent line to outer surface of separation function layer passing through reference point P Z2 tangent line to inner surface of separation function layer parallel to tangent line Z1 Z3 straight line bisecting the interval between Z1 and Z2

Claims

1. A composite semi-permeable membrane, comprising a porous support layer and a separation functional layer located on the porous support layer. The surface of the composite semi-permeable membrane has: a first surface, which is the surface facing the direction in which the separating functional layer exists relative to the porous support layer; and a second surface, which is the surface opposite to the first surface. The separation functional layer contains cross-linked polyamide. The cross-section of the separated functional layer along its thickness direction, as observed by a scanning transmission electron microscope, is divided into two equal parts: region a on the first surface and region b on the second surface. When the proportion of coarse pores with a diameter of 0.7 nm or more in region a is set as A, and the proportion of coarse pores with a diameter of 0.7 nm or more in region b is set as B, the ratio of A / B is less than 1.

40.

2. The composite semi-permeable membrane as described in claim 1, wherein, The proportion A of the coarse pores is less than 0.

10.

3. A composite semi-permeable membrane, comprising a porous support layer and a separation functional layer located on the porous support layer. The surface of the composite semi-permeable membrane has: a first surface, which is the surface facing the direction in which the separating functional layer exists relative to the porous support layer; and a second surface, which is the surface opposite to the first surface. The separation functional layer contains cross-linked polyamide. In the cross-section along the thickness direction of the separated functional layer, the ratio of carboxyl group density (Nd / Nf) measured by scanning transmission electron microscopy is less than 2.

1. Nd: Carboxyl group density in region d Nf: Carboxyl group density in region f Regions d and f: are regions included in regions c to g obtained by dividing the cross section of the separation functional layer in the thickness direction into five equal parts in the thickness direction of the separation functional layer, and regions c to g are arranged from the first surface toward the second surface.

4. The composite semi-permeable membrane as described in claim 3, wherein, The Nd is 2.3 × 10⁻⁶. -26 mol / nm 2 Below, and the Nf is 0.7 × 10 -26 mol / nm 2 above.

5. The composite semi-permeable membrane according to any one of claims 1 to 4, wherein, When the amount of terminal amino groups in the crosslinked polyamide is set to C, the amount of terminal carboxyl groups is set to D, and the amount of amide groups is set to E, E / (C+D) is 1.7 or higher.

6. The composite semi-permeable membrane according to any one of claims 1 to 4, wherein, The static contact angle of water on the surface of the separation functional layer is between 40 degrees and 120 degrees.

7. A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of claims 1 to 4.

8. A composite semipermeable membrane assembly comprising the composite semipermeable membrane element as described in claim 7.

9. A method for manufacturing a composite semi-permeable membrane, comprising a support membrane having a substrate and a porous support layer, and a separation functional layer disposed on the porous support layer. The separation functional layer is formed by interfacial condensation of a polyfunctional amine aqueous solution and a polyfunctional acyl halide solution in contact with the porous support layer. The polyfunctional amine aqueous solution comprises polyfunctional amines, monofunctional amines with a molecular weight of less than 150, and aqueous layer additives having amide or urea groups. The polyfunctional acyl halide solution comprises a polyfunctional acyl halide and an organic solvent.

10. The method for manufacturing the composite semi-permeable membrane as described in claim 9, wherein, The monofunctional amine has a molecular weight of less than 100.

11. The method for manufacturing the composite semi-permeable membrane as described in claim 9 or 10, wherein, The water content in the organic solvent is between 10 ppm and 50 ppm.

12. The method for manufacturing the composite semi-permeable membrane as described in claim 9 or 10, wherein, The concentration of the monofunctional amine in the aqueous solution of the polyfunctional amine is more than 0.01% by mass and less than 10% by mass.

13. The method for manufacturing the composite semi-permeable membrane as described in claim 9 or 10, wherein, The concentration of the aqueous layer additive in the polyfunctional amine aqueous solution is more than 0.01% by mass and less than 10% by mass.

14. A method for producing ultrapure water, comprising a reverse osmosis step of removing silica from an aqueous solution containing silica using a composite semi-permeable membrane as described in any one of claims 1 to 4.

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